I must echo Carol's words in an earlier post.
You really do need to work back logically from what you know for sure, confirming each step as you go.
You say you are pretty sure that your grandmothers maiden name was Stainer, from the birth index entries for her children.
Have you actually got any of these certs to confirm their mums name was Alice Maud Stainer? Or is that just an 'assumption' (Dont take any notice of whether it is spelt with an 'e' or not)
If not, getting your mother/father's birth cert would if my humble opinion be £7 well worth spending.
I did find 2 births for Alice Maud Stainers, and so IF that is the right Christian name and the right era, one MIGHT be your grandmother.
You say you have ruled out the 1899 one with parents Fred and Angelina - how have you ruled it out if you know absolutely nothing about the Stainer family?
I cant see the other one on a census to check on what brothers she had.
So, in order to prevent yourself either going mad with frustration or else settling for something that seems possible but might be absolutely nothing to do with your family at all, you are going to need to spend some money.
Looks like £3-50 for the Richard's war record, and £7 for mums birth cert will be good starters.
It may mean value beans on toast for dinner, or no Starbucks coffee for a while, but if you are serious about tracing finding out the truth about this great uncle of yours, I fear it is the only way.
LizDB